This invention concerns a pigment dispersant, more particularly, it concerns a pigment dispersant comprising an acrylic block copolymer, prepared by group transfer polymerization, in which one of the blocks is modified with a polar heterocyclic group to facilitate attachment to a pigment surface.
Acrylic block copolymer pigment dispersants prepared by group transfer polymerization (GTP) are known. Typically, such dispersants are of the AB, ABA or BAB types. All have at least one polar segment known as the A segment to facilitate attachment to a pigment surface, and at least one non-polar segment known as the B segment to enhance steric stabilization of the pigment particles in a dispersion and prevent flocculation. In addition, the A block may be modified with pendant polar groups for increased effectiveness, as for example, as taught in Hutchins et al. U.S. Pat. No. 4,656,226, issued Apr. 7, 1987. Such compositions can also be prepared with hydroxyl functional groups in the B segment to allow crosslinking in the final thermoset paint composition so that the dispersant will become part of the network structure; however, the dispersant properties may be negatively influenced.
Continued effort has been directed to improve the performance of pigment dispersants, and in particular to find a new class of acrylic block copolymer dispersants which are well suited for dispersing solid pigments in various liquid media, particularly solvent-borne paint systems.